What I ll talk about

Transcription

1 Brake Safety on the Road Deborah M. Freund Federal Motor Carrier Safety Administration Committee on Truck and Bus Safety Transportation Research Board Annual Meeting Washington, DC January 13, 2009 What I ll talk about Brake Sensors Mini-FOT Other Field Studies: PBBTs at roadside In-service assessment of CMV braking capability Smart Infrared Inspection System Bench Testing of SABAs Brake Adjuster Education/Outreach 2 1

2 What I ll talk about Brake Sensors Mini-FOT Other Field Studies: PBBTs at roadside In-service assessment of CMV braking capability Smart Infrared Inspection System Bench Testing of SABAs Brake Adjuster Education/Outreach 3 Purpose and Objectives How do systems perform? How reliable, durable, maintainable? Do systems influence maintenance practices? What are costs and benefits? Maintenance costs Component life Vehicle performance and safety 4 2

3 Fleet Characteristics Washington Metro Area Transit Authority Four Mile Run facility Orion VII urban transit buses, MY test and 12 control vehicles 300 sq mi service area in Arlington, VA Average travel 129 mi/day Average travel speed 16 mph Over 800,000 vehicle miles traveled during 12 months of data collection 5 Brake Sensors Commercially-available stroke monitors using Hall-effect sensors (2 makes) Strain gauged anchor pins (1 make) All are retrofittable to in-service vehicles All provide an in-cab display Data collected, devices checked weekly Buses tested monthly on a PBBT 6 3

4 7 Results: Brake Deficiencies 69 unsafe brake conditions identified 50 were confirmed faults 19 were false-positives (no visual validation) Only 1 complete sensor failure But other sensor faults due to wiring harness connections and loose sensors 8 4

5 Results: Brake Troubleshooting Both types of Hall-effect sensors identified a dragging brake condition on all buses Misalignment found between pushrod and slack adjuster Bus OEM resolved the situation Without this data, situation could have gone undetected for months! 9 Results: Technician Feedback Prognostics helped technicians quantify and reduce driver brake performance complaints WMATA and study team worked with suppliers to minimize system false positives and improve reliability Improved details on brake performance allowed WMATA to drop a hand-on 3,000- mile brake PM inspection. 10 5

6 What I ll talk about Brake Sensors Mini-FOT Other Field Studies: PBBTs at roadside In-service assessment of CMV braking capability Smart Infrared Inspection System Bench Testing of SABAs Brake Adjuster Education/Outreach 11 Role of PBBTs What a PBBT can do: Provide a rapid, objective and consistent measure of vehicle braking performance, irrespective of brake type, energy supply, or actuation method. What a PBBT cannot do: Replace inspector s skill in finding brake defects unrelated to immediate brake performance, such as air leaks, chafed hoses, or thin brake pads. 12 6

7 13 Use of PBBTs: Roadside Inspection Out-of-Service Criteria: Failing to develop a total brake force as a percentage of gross vehicle or combination weight of 43.5 or more on an approved PBBT. In the United States, an approved PBBT must meet the FMCSA functional specifications (65 FR 48799, August 9, 2000) 14 7

8 CMV Field Based Brake Wear and Performance Test Test site: Greene County, TN CMV inspection facility Vehicles selected from traffic stream Inspector-selected subset of vehicles directed to cross the permanent scale Level I brake-related inspection results and companion PBBT inspections February November 2008: 647 trucks (5,642 wheel ends) tested 15 Comparison: PBBT Results and Brake System Violations Pass PBBT Fail PBBT Pass NAS Level I Fail NAS Level I 57.3 % 10.4 % 20.9 % 11.4 % 16 8

9 Status Field data collection continues Long-term fleet vehicle data collection underway PBBT informational brochure and training video updated 17 In-service Assessment of CMV Braking Capability Q: Do CMVs still meet the 20 mph stopping distance test that 49 CFR requires? A: We need to do some testing the last field tests were done in

10 Results from first 38 vehicles 19 More results from first 38 vehicles 20 10

11 Smart Infrared Inspection System Sponsored by FMCSA Period of performance: September October 2009 Current activity: Ongoing update and testing of algorithms for automatic isolation of regions of interest Preliminary definition of possible rules to include in SIRIS software Hardware modifications (faster setup, improved detectors, higher-res color camera, etc.) Deployed 3 systems in field Defined statistical parameters for analysis 21 Some rules being considered Non/low functioning brakes Every wheel should have brake heat Grabbing or dragging brakes Brakes should not be super hot Overloaded, broken suspension, underinflated tire Tire sidewall should be cool Tire rubbing Tire tread should be cool Tire tread separation Tire tread temperature should be uniform Ungreased axle bearing or missing bearing cap Axle bearing cap should not be super hot 22 11

12 23 What I ll talk about Brake Sensors Mini-FOT Other Field Studies: PBBTs at roadside In-service assessment of CMV braking capability Smart Infrared Inspection System Bench Testing of SABAs Brake Adjuster Education/Outreach 24 12

13 Roadside Inspections: Brake Adjustment OOS Violations 60.0% 50.0% 40.0% 30.0% 20.0% 10.0% 0.0% Brake, Out of Adjustment OOS/Vehicle OOS Percent Brake, Out of Adjustment OOS/Total Brake OOS Percent 25 Current Practices related to SABAs survey to CVSA Associate Members and TMC members Current practice on air brake maintenance Awareness of proper procedures/warnings Key results: Many respondents are routinely adjusting SABAs (as if they are manual brake adjusters) More than half did not believe adjusting SABAs was a dangerous practice More than 60 percent were not aware of any warnings against manually re-adjusting SABAs 26 13

14 CVSA-sponsored study: What happens when SABAs are manually adjusted? Typical SABA adjustment procedure: Rotate adjusting nut clockwise until brake pads come in contact with drums Back adjusting nut off, counter-clockwise (CCW) ½ turn When rotating the adjusting nut CCW, internal mechanisms are subject to high forces Wear and potential damage can occur One type can be irreparably damaged with a single adjustment, if the manufacturer s warning and adjustment procedures are not followed 27 What happens to SABAs when manually adjusted? Method: 5 popular OEM SABAs were purchased off-the-shelf 28 14

15 Experiment SABAs were randomly selected and designated A through E. * Purpose was not to say Brand X is better than Brand Y Purpose was to quantify what happens to an ABA when manually adjusted, and How much adjustment can a typical SABA tolerate before it ceases to function properly? * - Please don t ask, because I don t know which is which 29 Bench-Top Setup Drive Motor Digital Torque Wrench Cycle Counter SABA Gear Reducer 30 15

16 Torque (ft-lbs) Torque (ft-lbs) Torque (ft-lbs) Torque (ft-lbs) Procedure Rotate adjustment nut CCW, periodically measure torque Compare measured torque to manufacturer s recommended minimum for proper operation Test duration: Assume lifetime of a vehicle is 10 years Vehicle is driven 300 days per year Adjustment made every time it is driven (150 CCW cycles per year) Total of 1500 CCW revolutions in vehicle lifetime 31 Nearly all SABAs lose torque after some amount of manual Results adjustment CCW Torque - Adjuster A (each point is Average of 11 measurements) 800 No. Revolutions CCW Torque - Adjuster B (each point is Average of 11 measurements) No. Revolutions CCW Torque - Adjuster C (each point is Average of 11 measurements) No. Revolutions CCW Torque - Adjuster D (each point is Average of 11 measurements) No. Revolutions Note: E was not tested because single rotation without releasing pawl causes immediate destruction. Releasing pawl causes no decrease in torque

17 What does this mean? Tests are preliminary Planning similar testing on aftermarket and knockoff SABAs Also planning to test using a complete wheel end assembly to more accurately assess interplay of all components (pending availability of resources). 33 What I ll talk about Brake Sensors Mini-FOT Other Field Studies: PBBTs at roadside In-service assessment of CMV braking capability Smart Infrared Inspection System Bench Testing of SABAs Brake Adjuster Education/Outreach 34 17

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19 Thank you very much! For further information, contact Luke Loy, Debbie Freund, Thanks for the photos: Battelle Memorial Institute Booz Allen Hamilton Oak Ridge National Labs 37 19